Generally, an automatic meter reading (AMR) installation may contain thousands, and possibly millions of metering devices distributed over a relatively large geographical area. Such devices are in many instances configured to exchange messages including data, for example, utility consumption data, with a cluster of servers including data metering collectors, and network management servers. AMRs are in some configurations organized around autonomous systems headed by cell relays, sometimes referred to as cell routers, where each autonomous system is connected to servers that may be located at the utility home office by way of a backhaul network. In certain such systems, Power Line Communication (PLC) systems may be employed to provide the backhaul network as well as to provide other system communications needs.
Power Line Communication (PLC) systems utilize the electrical infrastructure for carrying data. PLC systems may be used for communications over different segments of an overall power system, e.g., segments including high voltage transmission lines, medium voltage distribution networks, and lower voltages lines such as inside buildings. The ability of a communication system to deliver a certain amount of data per unit of time with limited number of errors is determined, at least in part, by the ratio of the energy contained in a data bit to the spectral density of noise within the channel bandwidth, i.e., the “Eb/No” ratio.
Unlike other communication systems, PLC links are often characterized by the voltage magnitude at the modem side of line couplers instead of being characterized by the power flow in the communication medium. An argument can be made that such approach is adequate, at least in certain instances, since from the transmitter side the highest drive level may be assumed to correspond to the maximum transmitted power while from the receiver side the signal-to-noise ratio seems to be independent from its notation since all signals (interferers and noise) are presented across the same line impedance, which consequently then does not need to be defined.
Alternatively, a counterargument is applicable because the transfer functions of line couplers are strongly affected by their associated complex line impedance. Thus, driving a transmitter to its maximum level may in fact be wasteful due to severe mismatch conditions between the coupler and the line. Considering the receiver side, a voltage-sensing receiver (i.e., a receiver having a high input impedance) may be connected to a long electrical conductor along with multiple mismatched loads and multiple sources of interference. In such a case, the aggregate voltage signal at any location represents a superposition of multiple voltage standing waves. Under such conditions, it is possible that a receiver might by happenstance be located in the minimum of a standing wave created by a strong transmitter while in the maximum of a standing wave created by a weak interference signal. Since the number of interference signals may be quite large, the probability of desired signals being blocked may remain high.
In view of such practical issues, it would be desirable to provide apparatus and methodologies whereby power line communications (PLC) signals may be received even in the presence of high noise levels. Nevertheless, while various aspects and alternative embodiments may be known in the field of power line communications, no one design has emerged that generally encompasses the above-referenced characteristics and other desirable features associated with power line communications technology as herein presented.